The non-Newtonian rheological properties of plastic melts are key factors in regulating plastic processing, molding and recycling processes, ensuring processing stability and product performance, and are the research focus in the field of plastic processing. The rheological basic data of commonly used plastics and their blend systems at present still need to be supplemented and improved. For this purpose, this study adopted a combined approach of experimental testing and theoretical modeling to investigate the rheological behaviors of four types of plastics, namely polypropylene (PP), polyethylene (PE), polystyrene (PS), and acrylonitrile-butadiene-styrene copolymer (ABS), as well as three binary blend systems of PE/ABS, PP/ABS, and PS/ABS. Rheological tests were conducted using a rheometer within the shear rate range of 0.1 s-1 to 100 s-1 and the temperature range of 180℃ to 250℃. The results indicated that the flow behavior index n of all samples was less than 1, and the apparent viscosity decreased significantly with the increase in shear rate, showing a clear shear thinning effect. Meanwhile, the consistency coefficient K changed with temperature in accordance with the Arrhenius relationship, and the melt viscosity decreased with the increase in temperature. This study quantitatively characterized the relationship between the mass fraction m (0.5<m≤1) of the main component in the binary blend systems and the melt viscosity. Based on the experimental data, a component correction term was introduced into the traditional power-law model to construct a constitutive equation that can simultaneously describe the effects of shear rate, temperature, and component fraction on melt viscosity. The average relative error between the model predictions and experimental values was only 5.90%. The rheological basic data and the modified constitutive equation obtained in this study can provide important theoretical support and data reference for the optimization of process parameters in fields such as waste plastic recycling and injection molding.